Study: Taking Antidepressants During Pregnancy Nearly Doubles the Risk of an Autism Diagnosis

Autism rates have risen sharply over the last decade. In 2000, one in 150 children was diagnosed with autism spectrum disorder. Today, that number has swelled to one in 68, according to the CDC. Factors such as better detection and awareness contribute to increase in diagnosis, but experts also believe there are environmental factors at play.

New research, published today in JAMA Pediatrics, may have unearthed one of them: antidepressant use during pregnancy.

The study, which followed more than 145,000 children from their conception to the age of 10, found that those born to mothers who had taken antidepressants during the second or third trimester of pregnancy were 87 percent more likely to be diagnosed with autism by age 7.

In total, based on mothers' prescription filling data, more than 4,700 infants were exposed to antidepressants in utero; of those, slightly over 2,500 were exposed during the second and/or third trimester. Using hospital records, the researchers then identified children who had received an autism spectrum diagnosis. "Finally, we looked for a statistical association between the two groups," Anick Bérard, the study's lead author, said in a statement. They found a significant one: Compared to children whose mothers had not taken antidepressants, or had only done so during the first trimester, these children were nearly twice as likely to receive an autism diagnosis. (Although, as autism experts not involved with the research have pointed out, because only 31 children developed autism in the study, the sample size is small enough that the risk factor is easily influenced by chance findings.)

Bérard speculated the association has to do with antidepressants' impact on brain development in the womb. "Serotonin is involved in numerous pre- and postnatal developmental processes," she said. "Some classes of anti-depressants work by inhibiting serotonin, which will have a negative impact on the ability of the brain to fully develop and adapt in-utero."

An estimated 13 percent of U.S. women take antidepressants at some point during their pregnancy. It’s important to note, however, that the implications of the JAMA Pediatric study do not mean there is a consensus among researchers about the link between antidepressants and autism.

One reason for uncertainty is the possibility that mothers with depression are more likely than nondepressed women to have children with autism, regardless of whether they take antidepressants during pregnancy.